Chemical Damp Proofing

Chemical damp proofing is a system which comprises of two main elements

The introduction of a water repellent or pore blocking material into a wall at a suitable level to form a continuous barrier against the capillary movement of water.

Re-plastering using a dense sand-cement base coat containing a water and salt resistant additive, followed by an additional sand-cement coat

Biocraft uses a range of Triton chemical damp proofing products. The Triton Triject injection system has a British Board of Agrement (BBA) certificate and Biocraft DPC installations are carried out in accordance with British Standard 6576:2005 Code of practice for installation of chemical damp proof courses and the current PCA code of practice for installation of remedial DPC’s in masonry walls.

Biocraft specifies water based chemical damp proofing products which are safer to use, have a very low odour and have much lower environmental burden then solvent based damp proofing chemicals.

Preparation for damp proofing
Preparatory works for damp proofing include the removal of skirting boards and radiators, damp, deteriorated or salt contaminated plaster, raking out mortar joints for re-plastering and exposing external face mortar joints if required. It is advisable to leave the internal walls exposed for as long as possible to promote drying.

Once the walls have been damp proofed and re-plastered the skirting boards are treated with a wood preservative and refitted.

Redecoration after damp proofing

It is advisable to allow the walls to dry out for as long as possible before redecoration following chemical damp proofing. After 3-4 weeks a coat of trade matt emulsion can be used although permanent decoration especially wallpapering should not be applied for 12 months or until such time as all residual moisture has dried out of the wall. Cracks in the new plaster should be filled with fine filler as part of the redecoration

Rule of thumb – a wall will dry out at the rate of 1” per month.

What to expect when you have a Damp proof course installed

Having chemical damp proofing installed can be a noisy and dusty job. Biocraft takes special care in minimise the disturbance caused to you and your neighbours. These are the steps that are involved in the installation of a chemical DPC;

Inform your neighbours prior to the start date (for neighbours that you share a wall with, “i.e. a party wall”, this is a legal requirement).

Clear the work area as much as possible, lift carpets, remove curtains and picture etc. All remaining items in the work area should be covered with protective film.

Seal doors in the work area that are not in use, to reduce the movement of dust.

Removing plaster and render for damp proofing

The required height of render to be removed will be marked and the plaster/render will be removed to this height leaving a straight clean edge for reinstatement of plaster.

The process of removing plasterwork is the noisiest and dustiest part of the job. The old plaster (spoil) will be removed from the work area and the area left clean for the DPC installation.

DPC installation

To install a chemical damp proof course (dpc), a series of holes will be drilled at a predetermined height and spacing throughout the area to be treated. In some cases, holes will be drilled in a vertical line to isolate adjoining untreated walls.

Depending on the damp proofing system, a low-pressure liquid damp proof course injection or gel damp proof course application will be used to insert the damp proofing product into the wall.

Biocraft installs its chemical DPC’s into the mortar bed, as this is the only continuous moisture pathway and external holes can be plugged without damaging the appearance of the property

How much does a chemical damp proof course cost?

The typical cost of a chemical damp proof course and damp proof re-plastering is £100-150/m2.

Biocraft carries out a comprehensive range of chemical damp proofing and damp control services throughout Berkshire, Hampshire, Surry and Oxfordshire.